Total Synthesis of (–)-Cordycicadin D and 3,4-trans-Cordycicadins A and B: Entry to the 3,4-trans-Fused Cordycicadin Framework
Bibliographic record
Abstract
Cordycicadins A–D are four C20 polyketides, all containing a gamma-lactone fused to a 10-membered lactone. The proposed biosynthetic pathway for the cordycicadins anticipates the formation of two more natural products which are unknown. We report the total synthesis of (–)-cordycicadin D and the two anticipated natural products 3,4-trans-cordycicadins A and B. The targets were convergently assembled, in a biomimetic fashion, via an efficient ketene trapping-intramolecular Michael addition sequence that delivered the requisite 3,4-trans-fused framework with high diastereoselectivity, enabled by the synthesis of complex dioxenones that serve as in situ ketene precursors. Recognition of the embedded polyketide symmetry enabled the use of a divergent-convergent synthetic stratergy, based on the use of two products from an early-stage enzymatic resolution. The synthetic routes afforded (–)-cordycicadin D in 14 steps and 3,4-trans-cordycicadins A and B in 13 steps (longest linear sequence). This work confirms the structure of (–)-cordycicadin D, and notes that observed instability of the anticipated natural product 3,4-trans-cordycicadin B during purification may explain why it is yet to be isolated.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".